Make "fsck-cache" use the same revision tracking structure as "rev-tree".

This makes things a lot more efficient, and makes it trivial to do things
like reachability analysis.

Add command line flags to tell what the head is, and whether to warn
about unreachable objects.

Author: Linus Torvalds

fsck-cache.c

@@ -3,114 +3,159 @@
 #include <sys/types.h>
 #include <dirent.h>
 
-struct needs {
-	unsigned char parent[20];
-	unsigned char needs[20];
-	char tag[10];
+/*
+ * The low 16 bits of the "flags" field shows whether
+ * a commit is part of the path to the root for that
+ * parent.
+ *
+ * Bit 16 is an internal flag that we've seen the
+ * definition for this rev, and not just seen it as
+ * a parent target.
+ */
+#define MAX_COMMITS (16)
+#define marked(rev)	((rev)->flags & 0xffff)
+#define SEEN 0x10000
+#define USED 0x20000
+#define REACHABLE 0x40000
+
+static int show_unreachable = 0;
+static int head_supplied = 0;
+static unsigned char head_sha1[20];
+
+struct parent {
+	struct revision *parent;
+	struct parent *next;
 };
 
-struct seen {
+struct revision {
+	unsigned int flags;
 	unsigned char sha1[20];
-	char tag[10];
-	unsigned needed;
+	unsigned long date;
+	struct parent *parent;
 };
 
-static struct needs *needs;
-static struct seen *seen;
+static struct revision **revs;
+static int nr_revs, rev_allocs;
 
-static int nr_seen, alloc_seen, nr_needs, alloc_needs;
-
-/*
- * These two functions build up a graph in memory about
- * what objects we've referenced, and found, and types..
- */
-static int compare_seen(const void *s1, const void *s2)
+static int find_rev(unsigned char *sha1)
 {
-	return memcmp(s1, s2, 20);
-}
+	int first = 0, last = nr_revs;
 
-static int lookup_seen(unsigned char *sha1, char *tag)
-{
-	int first = 0, last = nr_seen;
-
-	while (last > first) {
-		int next = (last + first) / 2;
-		struct seen *s = seen + next;
-		int cmp = memcmp(sha1, s->sha1, 20);
+	while (first < last) {
+		int next = (first + last) / 2;
+		struct revision *rev = revs[next];
+		int cmp;
 
+		cmp = memcmp(sha1, rev->sha1, 20);
+		if (!cmp)
+			return next;
 		if (cmp < 0) {
 			last = next;
 			continue;
 		}
-		if (cmp > 0) {
-			first = next+1;
-			continue;
-		}
-		if (strcmp(tag, s->tag))
-			break;
-		s->needed++;
-		return 1;
+		first = next+1;
+	}
+	return -first-1;
+}
+
+static struct revision *lookup_rev(unsigned char *sha1)
+{
+	int pos = find_rev(sha1);
+	struct revision *n;
+
+	if (pos >= 0)
+		return revs[pos];
+	
+	pos = -pos-1;
+
+	if (rev_allocs == nr_revs) {
+		rev_allocs = alloc_nr(rev_allocs);
+		revs = realloc(revs, rev_allocs * sizeof(struct revision *));
+	}
+	n = malloc(sizeof(struct revision));
+
+	n->flags = 0;
+	memcpy(n->sha1, sha1, 20);
+	n->parent = NULL;
+
+	/* Insert it into the right place */
+	memmove(revs + pos + 1, revs + pos, (nr_revs - pos) * sizeof(struct revision *));
+	revs[pos] = n;
+	nr_revs++;
+
+	return n;
+}
+
+static struct revision *add_relationship(struct revision *rev, unsigned char *needs)
+{
+	struct revision *parent_rev = lookup_rev(needs);
+	struct parent **pp = &rev->parent, *p;
+
+	while ((p = *pp) != NULL) {
+		if (p->parent == parent_rev)
+			return parent_rev;
+		pp = &p->next;
+	}
+
+	p = malloc(sizeof(*p));
+	p->parent = parent_rev;
+	p->next = NULL;
+	*pp = p;
+	return parent_rev;
+}
+
+static void mark_reachable(struct revision *rev)
+{
+	struct parent *p = rev->parent;
+
+	rev->flags |= REACHABLE | USED;
+	while (p) {
+		mark_reachable(p->parent);
+		p = p->next;
 	}
-	return 0;
 }
 
 static void check_connectivity(void)
 {
 	int i;
 
-	/* Sort the "seen" tags for quicker lookup */
-	qsort(seen, nr_seen, sizeof(struct seen), compare_seen);
+	if (head_supplied)
+		mark_reachable(lookup_rev(head_sha1));
 
 	/* Look up all the requirements, warn about missing objects.. */
-	for (i = 0; i < nr_needs; i++) {
-		struct needs *n = needs + i;
-		char hex[60];
+	for (i = 0; i < nr_revs; i++) {
+		struct revision *rev = revs[i];
 
-		if (lookup_seen(n->needs, n->tag))
+		if (show_unreachable && !(rev->flags & REACHABLE)) {
+			printf("unreachable %s\n", sha1_to_hex(rev->sha1));
 			continue;
-		strcpy(hex, sha1_to_hex(n->parent));
-		printf("missing %s: %s referenced by %s\n", n->tag, sha1_to_hex(n->needs), hex);
-	}
-
-	/* Tell the user about things not referenced.. */
-	for (i = 0; i < nr_seen; i++) {
-		struct seen *s = seen + i;
+		}
 
-		if (s->needed)
-			continue;
-		printf("unreferenced %s: %s\n", s->tag, sha1_to_hex(s->sha1));
+		switch (rev->flags & (SEEN | USED)) {
+		case 0:
+			printf("bad %s\n", sha1_to_hex(rev->sha1));
+			break;
+		case USED:
+			printf("missing %s\n", sha1_to_hex(rev->sha1));
+			break;
+		case SEEN:
+			printf("dangling %s\n", sha1_to_hex(rev->sha1));
+			break;
+		}
 	}
 }
 
 static void mark_needs_sha1(unsigned char *parent, const char * tag, unsigned char *child)
 {
-	struct needs *n;
-
-	if (nr_needs == alloc_needs) {
-		alloc_needs = alloc_nr(alloc_needs);
-		needs = realloc(needs, alloc_needs*sizeof(struct needs));
-	}
-	n = needs + nr_needs;
-	nr_needs++;
-	memcpy(n->parent, parent, 20);
-	memcpy(n->needs, child, 20);
-	strncpy(n->tag, tag, sizeof(n->tag));
+	struct revision * child_rev = add_relationship(lookup_rev(parent), child);
+	child_rev->flags |= USED;
 }
 
 static int mark_sha1_seen(unsigned char *sha1, char *tag)
 {
-	struct seen *s;
+	struct revision *rev = lookup_rev(sha1);
 
-	if (nr_seen == alloc_seen) {
-		alloc_seen = alloc_nr(alloc_seen);
-		seen = realloc(seen, alloc_seen*sizeof(struct seen));
-	}
-	s = seen + nr_seen;
-	memset(s, 0, sizeof(*s));
-	nr_seen++;
-	memcpy(s->sha1, sha1, 20);
-	strncpy(s->tag, tag, sizeof(s->tag));
-	
+	rev->flags |= SEEN;
 	return 0;
 }
 
@@ -160,7 +205,7 @@ static int fsck_commit(unsigned char *sha1, void *data, unsigned long size)
 		parents++;
 	}
 	if (!parents)
-		printf("root: %s\n", sha1_to_hex(sha1));
+		printf("root %s\n", sha1_to_hex(sha1));
 	return 0;
 }
 
@@ -237,8 +282,20 @@ int main(int argc, char **argv)
 	int i;
 	char *sha1_dir;
 
-	if (argc != 1)
-		usage("fsck-cache");
+	for (i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--unreachable")) {
+			show_unreachable = 1;
+			continue;
+		}
+		if (!get_sha1_hex(argv[i], head_sha1)) {
+			head_supplied = 1;
+			continue;
+		}
+		usage("fsck-cache [[--unreachable] <head-sha1>]");
+	}
+	if (show_unreachable && !head_supplied)
+		usage("unable to do reachability checks without a head");
+
 	sha1_dir = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
 	for (i = 0; i < 256; i++) {
 		static char dir[4096];